Preparation of Bromine-Containing Polymers Useful as Flame Retardants

ABSTRACT

The invention relates to a process for preparing bromine-containing polymer, comprising a Friedel-Crafts alkylation reaction of tetrabromoxylylene dihalide, or tetrabromoxylylene dihalide in combination with pentabromobenzyl halide, with a reactant having one or more six-membered aromatic rings, wherein the reaction takes place in a solvent in the presence of a Friedel-Crafts catalyst, and isolating from the reaction mixture the bromine-containing polymer. The so-formed polymers and their use as flame retardants form additional aspects of the invention.

Brominated compounds are known to be highly effective as flameretardants, and in many cases they constitute the only possible optionfor reducing the fire risk of synthetic materials. It is postulated thatthe higher the molecular weight of the brominated flame retardant, thelower is its volatility and its ability to bio-accumulate in livingtissues. Therefore, there exists a need to develop high molecularpolymeric brominated flame retardants.

The present invention relates to a class of polymers with abromine-containing repeat unit along the polymer chain, and withbromine-containing side groups. The repeat unit of the polymer comprisesat least one of the three isomers depicted below:

(also identified herein by the chemical formula —CH₂C₆Br₄CH₂—). Thestructural units depicted above are obtained from correspondingdi-halide difunctional monomers, i.e., HalCH₂C₆Br₄CH₂Hal(tetrabromoxylylene dihalide), where Hal independently indicates halogenatom such as chlorine or bromine.

The polymers of the invention further contain side groups consisting ofpentabromobenzyl groups. Hereinafter, the pentabromobenzyl group issometimes described by means of its molecular formula —CH₂C₆Br₅ or itsmolecular structure:

In EP 305196, there is reported the preparation of bromine-richcompounds by the reaction of the aforementioned difunctional monomerHalCH₂C₆Br₄CH₂Hal with a trifunctional monomer which is2,4,6-trihydroxy-s-triazine, known as (iso)cyanuric acid, in thepresence of pentabromobenzyl bromide. More specifically, Example 5 of EP305195 describes the dissolution of a mixture consisting of 0.3 moltetrabromoxlilydene dibromide and 0.3 mol pentabromobenzyl bromide indimethylformamide (DMF), followed by the addition of the trisodium saltof (iso)cyanuric acid (0.2 mol). The thermal stability of the so-formedpolymer was characterized by means of thermogravimetric analysis (TGA),which measures the weight loss of a sample as sample temperature isincreased (in air, at heating rate of 10° C./minute). The data set outin Example 5 of EP 305196 is tabulated below:

TABLE A temperature T1 = 275° C. T2 = 337° C. T3 = 375° C. % weight loss2.0 5.0 10.0

It is seen that the thermal stability of the polymer product of Example5 of EP 305196 is not entirely satisfactory.

We have now found a synthetic route for incorporating into a polymerstructure, the bromine-containing group —CH₂C₆Br₄CH₂—, preferablytogether with the —CH₂C₆Br₅group, thereby forming bromine-rich polymersdisplaying good thermal stability. The synthetic route involveselectrophilic C-alkylation of aromatic rings with the bi-functionalcompound HalCH₂C₆Br₄CH₂Hal, in the presence of a Friedel-Craftscatalyst, to form polymer chain(s). An Addition of HalCH₂C₆Br₅to thereaction mixture, either simultaneously with, or consecutively to, theaddition of HalCH₂C₆Br₄CH₂Hal, results in the introduction of the—CH₂C₆Br₅ as side groups onto the aromatic rings in the polymerchain(s), increasing the bromine content of the product. The so-formedpolymers of the invention, which contain the pentabromobenzyl andtetrabromoxylylene groups, have high molecular weight (>3000), theirbromine content is preferably not less than 70%, they are insoluble inwater and are also quite stable against hydrolysis and/or decomposition.

Accordingly, the present invention provides a novel class of polymers,with —CH₂C₆Br₄CH₂— and A units arranged alternately along the polymerbackbone chain:

≈≈CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A≈≈

wherein A consists of one or more six-membered aromatic rings (the wavylines indicate the extension of the polymer chain). Preferably, thereare additionally —CH₂C₆Br₅ side groups attached to at least a portion ofthe six-membered aromatic rings of the backbone chain.

The growth of the polymer backbone chain occurs by the formation of abond between one aliphatic carbon of a —CH₂C₆Br₄CH₂— unit and a carbonatom of an aromatic ring of a first A unit, and an additional bond,between the second aliphatic carbon atom of the same —CH₂C₆Br₄CH₂— unit,and a carbon atom of an aromatic ring of a second A unit, and so forth.Likewise, a bond is formed between a carbon atom of an aromatic ring andan aliphatic (benzylic) carbon of the —CH₂C₆Br₅ group, to afford theside groups. Hereinafter, the term ‘pendent groups’ indicates the—CH₂C₆Br₅ groups bonded to the aromatic rings of the polymer chain.

It should be noted that the polymers of the invention are notnecessarily linear, as three —CH₂C₆Br₄CH₂— groups may become bonded tothe same A unit, to produce a branched polymer. In each of the branchesof the polymer, —CH₂C₆Br₄CH₂— and A units are arranged alternately alongthe branch, preferably with pendent —CH₂C₆Br₅.

The compounds of the inventions are therefore composed of chainsdescribed by the following formula P:

wherein n is the number of repeat units (e.g., 3<n<300); Ar indicates astructure comprising one or more six-membered aromatic ring(s),characterized in that at least one carbon atom of said six memberedaromatic ring(s) is bonded to a methylene carbon of the —CH₂C₆Br₄CH₂—group; where x, which indicates the number of —CH₂C₆Br₄CH₂— moieties inthe unit, is equal to or greater than 1; and y, which indicates thenumber of —CH₂C₆Br₅ pendent groups in the repeat unit, is equal to orgreater than 0.

Preferably, Ar contains one six-membered aromatic ring, or two,preferably non-fused, six-membered aromatic rings, and y is at leastequal to the number of the aromatic rings in Ar, e.g., y is 1, 2, 3, or4. For example, is Ar contains one aromatic ring, then the number of—CH₂C₆Br₅ pendent groups would preferably be 1 or 2. If Ar contains twoaromatic rings, then the number of the —CH₂C₆Br₅ pendent groups wouldpreferably be 3 or 4. It should be noted that each of the six-memberedaromatic ring(s) of which Ar is composed may be substituted, e.g., byalkyl group(s). When Ar consists of two six-membered aromatic rings,then these rings may be either connected by bridges selected from thegroup consisting of alkylene chains, —O— or —S—, or said rings may bedirectly joined to each other by a single bond.

More specifically, the present invention provides a novel high molecularweight polymer compound having chains with repeat units represented byFormula (I), and/or a mixture of such compounds:

In formula (I), R is a linear or branched aliphatic chain; k is aninteger from 0 to 3; a₁ and a₂ are independently an integer from 1 to 3,preferably 1; b₁ and b₂ are independently an integer from 1 to 3,preferably 1 or 2; m is 0 or 1; a₁+b₁≦3 and a₂+b₂≦3, such that a₁+m·a₂equals x (Formula P), and b₁+m·b₂ equals y (Formula P); Z is selectedfrom the group consisting of null, O, S and a linear or branchedalkylene, e.g., an alkylene group containing 1 to 10 carbon atoms.

The compounds of the invention are prepared by reacting atetrabromoxylylene dihalide [HalCH₂C₆Br₄CH₂Hal] either alone or incombination with pentabromobenzyl halide [HalCH₂C₆Br₅], with a startingmaterial which comprises at least one six-membered aromatic ring, as setout above, in the presence of a Friedel-Crafts catalyst (Lewis acids)such as AlCl₃, AlBr₃, GaCl₃, FeCl₃, SnCl₄, SbCl₃, ZnCl₂, CuCl₂ and HF,preferably AlCl₃.

Thus, the invention relates to a process for preparingbromine-containing polymer, comprising a Friedel-Crafts alkylationreaction of tetrabromoxylylene dihalide, or a combination oftetrabromoxylylene dihalide and pentabromobenzyl halide, with a reactanthaving one or more six-membered aromatic rings in a solvent, in thepresence of a Friedel-Crafts catalyst, and isolating bromine-containingpolymer from the reaction mixture.

The preferred tetrabromoxylylene dihalide for use in the invention istetrabromo-para-xylylene dihalide, especially tetrabromo-para-xylylenedibromide (chemically namedα,α′-(dibromomethyl)-2,3,5,6-tetrabromoxylene, abbreviated hereinTBX-DB). The compound is commercially available from ICL-IP and AcesPharma Inc. TBX-DB can be produced according to the route of synthesisinvolving the aromatic bromination of para-xylene, for example inhalogenated solvent(s), using elemental bromine, in the presence of aLewis acid catalyst, e.g. AlCl₃, to form tetrabromoxylene, which is thenbrominated at the benzylic carbons using elemental bromine and a radicalsource e.g. azobisisobutyronitrile, as illustrated by the scheme:

According to U.S. Pat. No. 3,899,466, the other isomers,tetrabromo-meta-xylylene dibromide and tetrabromo-ortho-xylylenedibromide, are prepared by the same process.

The preferred pentabromobenzyl halide for use in the invention ispentabromobenzyl bromide (chemically named1-(bromomethyl)-2,3,4,5,6-pentabromobenzene and abbreviated hereinPBBBr). It is commercially available from ICL-IP, or can be prepared bymethods known in the art (e.g., U.S. Pat. No. 6,028,156 and U.S. Pat.No. 7,601,774), according to the route of synthesis involving thearomatic bromination of toluene, for example in halogenated solvent(s),using elemental bromine, in the presence of a Lewis acid catalyst, e.g.AlCl₃, to form pentabromotoluene (abbreviated herein 5-BT), which isthen brominated at the benzylic carbon using elemental bromine and aradical source e.g. azobisisobutyronitrile, as illustrated by thefollowing scheme (see U.S. Pat. No. 7,601,774):

Regarding the preferred starting material which undergoes the aromaticsubstitution reaction, namely, the electrophilic C-alkylation, itcontains one six-membered aromatic ring, or two, preferably non-fused,six-membered aromatic rings. Preferably, this reactant is represented byFormula (II):

In formula (II) R a linear or branched aliphatic chain; k is an integerfrom 0 to 3; m is 0 or 1; Z is selected from the group consisting ofnull, O, S and a linear or branched alkylene, e.g., an alkylene groupcontaining 1 to 10 carbon atoms.

Exemplary starting materials of Formula II include:

-   -   Toluene, where R═CH₃, k=1, m=0;    -   Xylene, where R═CH₃, k=2, m=0;    -   Ethylbenzene, where R═C₂H₅, k=1, m=0;    -   Diphenyl ether, where k=0, Z═O, m=1;    -   Diphenylmethane, where k=0, Z═—CH2—, m=1; and    -   1,2-Diphenylethane, where k=0, Z═—(CH2)2—, m=1.

The Friedel-Crafts alkylation reaction according to the invention takesplace in a solvent or a mixture of solvents, e.g., in a halogenatedaliphatic hydrocarbon which is preferably selected from the groupconsisting of dichloromethane (DCM), dibromomethane (DBM),bromochloromethane and dichloroethane (DCE). The molar ratio between thethree reactants is suitably adjusted to satisfy the desired degree ofsubstitution on the six-membered aromatic ring(s) and the length of thepolymer chain. In general, it is desired to attach not less than one—CH₂C₆Br₄CH₂— group, and preferably two —CH₂C₆Br₅ groups to eachsix-membered aromatic ring present in the starting material. The amountof catalyst, e.g., AlCl3, is preferably between 0.5% wt/wt and 2% wt/wtrelative to the amount of PBBBr. The reaction is carried out underanhydrous conditions.

When HalCH₂C₆Br₄CH₂Hal (e.g., TBX-DB) is used as the sole alkylatingreagent to produce polymers devoid of pendent groups, then the reactionis accomplished by dissolving the aromatic starting material and TBX-DBin the solvent under heating, followed by addition of the catalyst. Ifboth HalCH₂C₆Br₄CH₂Hal and HalCH₂C₆Br₅ (e.g. TBX-DB and PBBBr,respectively) are used in the Friedel-Crafts alkylation reaction, thensaid two alkylating reagents may be fed to the reaction vessel eithersimultaneously or successively. A simultaneous mode of addition wouldnormally lead to the formation of a polymer dominated by a linearskeletal structure. A successive mode of addition, wherein the feedingof HalCH₂C₆Br₅ is initiated only after an added amount of the startingmaterial of Formula II had been at least partially consumed by areaction with HalCH₂C₆Br₄CH₂Hal, would lead to the formation of branchedpolymers. For example, one convenient way of putting the successivefeeding mode into practice involves charging a reaction vessel with thestarting material of Formula II and HalCH₂C₆Br₄CH₂Hal, and ondisappearance of said HalCH₂C₆Br₄CH₂Hal, adding HalCH₂C₆Br₅, or amixture of HalCH₂C₆Br₄CH₂Hal and HalCH₂C₆Br₅.

Irrespective of the mode of addition of the reactants, the reaction isallowed to reach completion at a temperature in the range from 40°C.-90° C. In general, the reaction time is from 2 to 8 hours. TheFriedel-Crafts alkylation reaction is accompanied by the generation ofhydrogen bromide. The end of the reaction is indicated by the completeconsumption of the either PBBBr, TBX-DB or both. Their disappearance maybe determined either by gas chromatography analysis or by the cessationof hydrogen bromide evolution.

The product is isolated from the reaction mixture by means ofconventional techniques. The reaction mixture is repeatedly washed withaqueous sodium bisulfite (SBS) solution and water, whereby the excesscatalyst is destroyed. The polymer product is virtually insoluble insome of the solvents used, for example in DCE, and precipitates almostinstantly from the liquid reaction mass. The solid is then separatedfrom the liquid phase by filtration. However, if the formed product issoluble, at least to some extent, in the reaction solvent, (for example,in DBM), then it is caused to precipitate by the addition of anon-solvent, i.e., a solvent in which the product is essentiallyinsoluble. For example, a lower alcohol such as isopropanol, which ismiscible with the halogenated reaction solvent, is useful as anon-solvent for precipitating the product. The isolated product can thenbe heated in dichloromethane under stirring for at least one hour. Theslurry is cooled and the solid product is collected by filtration, andoptionally washed and dried.

The invention also relates to the use of HalCH₂C₆Br₄CH₂Hal andHalCH₂C₆Br₅ (e.g. TBX-DB and PBBBr, respectively) as alkylation reagentsin the Friedel-Crafts alkylation of the compounds of Formula II. In apreferred embodiment, the invention provides a process comprisingcharging a reaction vessel with a solvent (e.g., halogenated aliphatichydrocarbon), a starting material of Formula II (e.g., toluene or1,2-diphenylethane), the combination of HalCH₂C₆Br₄CH₂Hal andHalCH₂C₆Br₅, reacting same in the presence of a catalyst (e.g. aluminumchloride) and recovering a Friedel-Crafts alkylation product.

In one preferred class of the polymer compounds of the invention ofFormula P, Ar is toluene. This class of compounds is more specificallyrepresented by Formula I, where m=0, R is CH₃ and k is 1, especially apolymer with repeat units of Formula I with a1=b1=1. Therefore, theinvention preferably provides polymers with chains represented byFormula III (where n is the number of repeat units; e.g., 3<n<300):

The polymer of Formula III is prepared by the Friedel-Crafts alkylationreaction depicted below, where the aromatic starting material istoluene:

In another preferred class of polymer compounds of the invention ofFormula P, Ar is selected from the group consisting of diphenylether,diphenylmethane and 1,2-diphenylethane; this class of compounds isrepresented by Formula I, wherein k=0 and m=1. Therefore, the inventionpreferably provides polymers with chains having repaet units representedby Formula IV:

wherein Z is selected from the group consisting of 0, —CH₂—, and—CH₂—CH₂—, said compounds having bonds between carbon atoms of thearomatic rings of the diphenyloxide or diphenylalkane moieties and thealiphatic carbon of the —CH₂C₆Br₄CH₂— group, with al and a2 beingindependently either 1, 2 or 3 (preferably each of a1 and a2 equals 1);and also with the aliphatic (benzylic) carbon of the —CH₂C₆Br₅ group,with b1 and b2 being independently 0, 1 or 2, (preferably each of b1 andb2 equals 2). The bromine content of the compound is preferably not lessthan 60%, e.g., in the range from 60 to 75%. Bromine content of theproduct is measured by the Parr Bomb method, involving the decompositionof bromine-containing organic compounds to give bromides, followed byargentometric titration, as described further below.

More preferred are compounds of Formula IV wherein z is —CH₂—CH₂—,having a bromine content of not less than 66% by weight (if b1=b2=0),e.g., in the range from 66 to 75% by weight (the upper limit correspondsto b1=b2=2), especially the polymer with b1=b2=2. Preferably, theinvention provides polymers with chains represented by Formula V (wheren is the number of repeat units; 3<n<300):

The polymer of Formula V is prepared by the Friedel-Crafts alkylationreaction depicted below:

The thermal stability profile of preferred polymers of the invention, asindicated by thermogravimetric analysis (TGA), which measures the weightloss of a sample as sample temperature is increased (in nitrogen, atheating rate of 10° C/minute), is typically as follows:

temperature T1 ≧330° C. T2 ≧360° C. T3 ≧380° C. % weight loss 2.0 5.010.0

The bromine-rich polymers of the invention are useful as flame retardantagents in a flammable material. Accordingly, another aspect of thepresent invention is a flame-retarded formulation which comprises aflammable material and the novel polymer of the invention. For example,the bromine-containing polymers of the invention are especially usefulfor reducing the flammability of styrene-containing polymers such ashigh impact polystyrene (HIPS) and acrylonitrile-butadiene-styrenecopolymer (ABS).

A flame-retarded formulation of the invention comprises an effectiveflame-retarding amount of the novel bromine-containing polymer of theinvention, e.g., the compounds of Formula I, especially of Formulas IIIand V. The concentration the bromine-containing polymer of the inventionin the plastic formulation is adjusted to secure a bromine content ofleast 5 wt %, and preferably at least 10 wt %, e.g., from 5 to 15 wt %(relative to the total weight of the plastic formulation).

Other conventional additives may also be included in the formulation.For example, an inorganic compound (typically a metal oxide) capable ofcooperating with the novel bromine-containing polymer is preferably alsoincorporated into the formulation. A preferred example of a suitableinorganic compound, which is generally considered as an “inorganicsynergist”, is antimony trioxide.

Additionally, the polymer formulation of this invention may containlubricants, antioxidants (e.g., of a hindered phenol or phosphite type),pigments, UV stabilizers and heat stabilizers. The concentration of eachof the conventional additives listed above is typically in the rangebetween 0.05 and 10 wt %.

The plastic formulations which are flame-retarded with the aid of thecompounds of the invention are readily prepared by methods known in theart. The various ingredients of the formulation are blended together,according to their respective amounts. The ingredients may be first dryblended using suitable mixing machines, such as Henschel mixer. Theresulting mixture may then be processed and compounded to formhomogeneous pellets, for example, by using a twin screw extruder. Thepellets obtained are dried, and are suitable for feed to an articleshaping process such as injection molding. Other blending and shapingtechniques can also be applied. Articles molded from the polymerformulations form another aspect of the invention.

For example, the polymer of Formula III:

has been successfully added at a fairly reasonable amount to HIPS toachieve UL-94 V-0 rating. Accordingly, a specific aspect of theinvention is HIPS composition comprising HIPS resin andbromine-containing polymer of Formula I, especially of Formula III. HIPSresins suitable for use in the invention are the rubber-modifiedcopolymers or homopolymers of styrenic monomers, obtainable, forexample, by mixing an elastomer (butadiene) with the (optionallysubstituted) styrenic monomer(s) prior to polymerization.Characteristics and compositions of HIPS are described, for example, in“Encyclopedia of Polymer Science and Engineering”, Volume 16, pages88-96 (1985). The HIPS formulations provided by the invention generallycomprise not less than 50 wt % HIPS resin, e.g., between 50 and 95 wt %,and preferably between 70 and 90 wt % HIPS resins (such as HIPS resinshaving a melt flow index (MFI) between 1 and 50 g/10 min (ISO 1133; 200°C./5 kg)). HIPS resins which are suitable for use according to theinvention are commercially available from various manufacturers, forexample Dow Styrone or INEOSNOVA Empera.

The HIPS formulation according to the present invention furthercomprises from 10 to 20% by weight (for example, from 12 to 18%) of thebromine-containing flame retardant of Formula I (e.g., of Formula III),from 1.0 to 5.0% by weight (for example, from 1.5 to 2.5%) antimonytrioxide and one or more anti-dripping agents such aspolytetrafluoroethylene (abbreviated PTFE) in a preferred amount between0.025 and 0.4 wt %, more preferably between 0.025 and 0.3 wt %, and evenmore preferably between 0.05 and 0.2 wt %. PTFE is described, forexample, in U.S. Pat. No. 6,503,988.

In yet another embodiment of the invention, the polymer of Formula V:

has been successfully used to reduce the flammability of ABS (with theaid of antimony trioxide). ABS compositions of the invention preferablycomprise not less than 50 wt % ABS (relative to the total weight of theformulation), e.g., from 50 to 85 wt % ABS. The term ABS refers in thecontext of the present invention to copolymers and terpolymers thatinclude the structural units corresponding to (optionally substituted)styrene, acrylonitrile and butadiene, regardless of the composition andmethod of production of said polymers. Characteristics and compositionsof ABS are described, for example, in the Encyclopedia of PolymerScience and Engineering, Volume 16, pages 72-74 (1985). ABS with MFIbetween 1 and 50 g/10 min (measured according to ISO 1133 at 220° C./10kg) are used.

The ABS formulation according to the present invention also comprisesfrom 5 to 20% by weight (for example, from 10 to 18%) of thebromine-containing flame retardant of Formula I (e.g., of Formula V),from 1.0 to 6.0% by weight antimony trioxide (for example, from 1.5 to5.0%) and one or more anti-dripping agents such as PTFE in a preferredamount between 0.025 and 0.4 wt %, more preferably between 0.025 and 0.3wt %, and even more preferably between 0.05 and 0.2 wt %.

Polypropylene formulation of the invention preferably comprises apolypropylene copolymer in an amount of not less than 50 wt % (relativeto the total weight of the formulation), e.g., from 50 to 85 wt %.Suitable polypropylene impact copolymers which can be used in thepresent invention can be in the form of block copolymers comprising afirst block (or phase), which is essentially the polypropylenehomopolymer component and a second block (or phase), which is anethylene-propylene copolymer component. A polypropylene impact copolymeris produced by means of sequential polymerization reactions underconditions known in the art. The first reaction produces the homopolymercomponent and the second reaction produces the copolymer component.Thus, the copolymer component is chemically incorporated within thematrix of the homopolymer component. Different grades of polypropyleneimpact copolymers in the form of block copolymers are commerciallyavailable (Carmel Olefins, Israel, under the name Capilene® SE 50E, TR50 and SL 50). Impact modified polypropylenes can be prepared byadmixing a polypropylene homopolymer and a rubber. The compounds of theinvention can be used to reduce the flammability of either filler-freeor filler-containing polypropylene-based formulations.

Polyamide-based formulation of the invention comprises at least 30%polyamide, e.g., between 40% and 70% wt %. The polyamide formulationfurther comprises reinforcing fillers, namely, glass fibers, which aretypically pre-coated prior to their use by methods known in the art inorder to improve their compatibility with the polyamide matrix. Suchmodified forms of glass fibers are available in the market, e.g., GFChop Vantage 3660 from PPG. The glass fibers comprise filaments withdiameters in the range from 2μ to 20μ, and are applied in the form ofpieces with lengths in the range from 2 to 10 mm, e.g., from 3 to 4.5mm. For example, the major constituents of glass fibers applied forreinforcing polyamide are alumino-borosilicates; such a type of glass isknown as E-glass. The concentration of the glass fibers is from 5% to40% of the total weight of the polyamide composition.

The polyamide compositions are produced by melt-mixing the components,e.g., in a co-kneader or twin screw extruder, wherein the mixingtemperature is in the range from 200 to 300° C. For example, thepolyamide, the bromine containing flame retardant and the conventionaladditives (with the exception of the glass fibers) are dry blended andthe blend is fed to the extruder throat. The glass fibers are the lastto be added, i.e., downstream.

Articles molded from the polymer formulations which are flame retardedwith the bromine-containing polymers form another aspect of theinvention.

EXAMPLES Methods

TGA Analysis:

The TGA analysis was performed by a Mettler-toledo instrument model 850.˜10 mg sample were heated in aluminum oxide crucible from 35 to about700° C. with heating rate of 10° C./min in nitrogen atmosphere.

Bromine Content:

Bromine content of the compounds is measured by the Parr Bomb method.The sample (˜0.08-0.12 g) is placed in a peroxide bomb vessel. Sucrose(0.5 g) is added and the full dipper of sodium peroxide is also added.The sample is subjected to oxidizing with sodium peroxide while a burnerflame is applied to the bottom of the bomb; the bomb is heated up toabout 200° C. and the burner is then turned off. The bomb is placed incold water (2 liters). Gaseous products are absorbed by the alkalinemixture and are retained within the bomb, mostly in the form of sodiumbromide. The content of the bomb is then combined with warm water.Hydrazine sulfate is added to destroy residual sodium peroxide. Nitricacid is added in portions, until the solution is completely neutralizedand becomes acidic. The solution is cooled to room temperature and thensubjected to titration with AgNO3 (0.1 N) to determine bromine content.

Example 1 Reaction of Toluene with PBBBr and TBX-DB

DCE (300 ml), PBBBr (84.8 g, 0.15 mol), TBX-DB (66.1 g, 0.114 mol), andtoluene (13.8 g, 0.15 mol) were placed in a 500 ml reactor fitted with amechanical stirrer, thermometer, condenser, HBr trap and N2 inlet. Themixture was heated to 60° C. AlCl3 (1.3 g, 0.01 mol) was added byportions and the vigorous formation of HBr started. The mixture was keptat 60° C. for 2-4 hours until the PBBBr and TBX-DB disappeared (detectedby GC and HBr evolution). The reaction mixture was washed three timeswith water (3×300 ml) and an aqueous solution of NaHCO3, taking 30minutes for each washing. The reaction mixture was cooled to 50° C. andthe solid was filtered off and dried in an oven at 150° C. under reducedpressure for 24 hours, giving 131.3 g, corresponding to an ˜98% yield.The content of bromine was about 70%.

The TGA profile of the so-formed product is tabulated below:

Temperature T1 = 360° C. T2 = 398° C. T3 = 415° C. % weight loss 2.0 5.010.0

Example 2 Reaction of Ttoluene with PBBBr and TBX-DB

The procedure of Example 1 was repeated, but a solution of DCE (35 ml)and toluene was added dropwise over 1.5 h. The weight of the product was132.5 g, corresponding to ˜99% yield. The content of bromine was about69.0%.

Example 3 Reaction of Toluene with PBBBr and TBX-DB

The procedure of Example 1 was repeated, using DBM (1.25 l) instead ofDCE, PBBBr (424.1 g, 0.75 mol), TBX-DB (312.9 g, 0.54 mol), toluene(69.1 g, 0.75 mol), and AlCl₃ (1.3 g, 0.01 mol). After washing, thesuspension of the product was added dropwise to IPA (iso-propyl alcohol)(3.5 l), stirred at 20° C. for 30 min and the product was filtered off.The weight of the dried product was 642.0 g, corresponding to ˜97%yield. The content of bromine was about 72%.

Example 4 Reaction of Toluene with PBBBr and TBX-DB

The procedure of Example 1 was repeated using DBM (250 ml) instead ofDCE, PBBBr (84.8 g, 0.15 mol), TBX-DB (62.6 g, 0.108 mol), toluene (13.9g, 0.15 mol), and AlCl₃ (0.8 g, 0.006 mol). The PBBBr was added afterthe added TBX-DB had disappeared (about 1.5 h). After washing, thesuspension of the product was added dropwise to IPA (700 ml), stirred at20° C. for 30 min and the product was filtered off. The weight of theproduct was 127.8 g, corresponding to ˜96% yield. The content of brominewas about 71%.

Example 5 Reaction of Diphenylethane with PBBBr and TBX-DB

The procedure of Example 1 was repeated, but using DBM (250 ml) insteadof DCE, diphenylethane instead of toluene (9.1 g, 0.05 mol), PBBBr(113.1 g, 0.2 mol), TBX-DB (20.3 g, 0.035 mol), and AlCl₃ (0.8 g, 0.006mol). After washing, the suspension of the product was added dropwise toIPA (1000 ml), stirred at 20° C. for 30 min and the product was filteredoff. The weight of the product was 114.8 g, corresponding to ˜94% yield.The content of bromine was about 75%. In view of the bromine content,the product is assigned with the following structure:

The TGA profile of the product is tabulated below:

Temperature T1 = 343° C. T2 = 371° C. T3 = 391° C. % weight loss 2.0 5.010.0

Example 6 Reaction of Diphenylethane with TBX-DB

The procedure of Example 1 was repeated, but using diphenylethaneinstead of toluene (10.9 g, 0.06 mol), TBX-DB (104.3 g, 0.18 mol), DCM(250 ml) and AlCl₃ (1.1 g, 0.09 mol). The weight of the product was 89.6g. The content of bromine was about 66%.

Example 7 Reaction of Diphenyloxide with PBBBr and TBX-DB

The procedure of Example 5 was repeated, but using diphenyloxide insteadof diphenylethane (8.5 g, 0.05 mol). The weight of the product was 115.1g, corresponding to an ˜96% yield. The content of bromine was about 75%.

Example 8 Reaction of Diphenylmethane with PBBBr and TBX-DB

The procedure of Example 5 was repeated, but using diphenylmethaneinstead of diphenylethane (8.4 g, 0.05 mol). The weight of the productwas 113.0 g, corresponding to an ˜94% yield. The content of bromine wasabout 75%.

In the studies reported in the following examples, the ability ofbromine-containing polymers of the invention to reduce the flammabilityof different thermoplastic was evaluated. Test specimens were preparedand subjected to a flammability test according to theUnderwriters-Laboratories standard UL 94, applying the vertical burn onspecimens of 0.8, 1.6 mm or 3.2 mm thickness.

Examples 9 to 11 V-1 and V-0 Rated HIPS Formulations

In this set of examples, the compound of Formula III (the product ofExamples 1 and 3) was tested to evaluate its ability to reduce theflammability of HIPS.

Ingredients Used to Prepare the Compositions

The materials employed in the experimental work are set out in Table 1(the abbreviation “FR” indicates flame retardant):

TABLE 1 Product (manufacturer) description function Styron 1200 Highimpact polystyrene plastic matrix (Dow) Product of Examples 1, 3

FR AO 0112 Antimony trioxide masterbatch FR-synergist (Kafrit) whichcontains 80% by weight Sb₂O₃ Hostaflon 2017 PTFE Anti-dripping agent(Dyneon) Irganox B-225 50% tris(2,4-ditert- Antioxidant & heat (Ciba)butylphenyl)phosphite and 50% stabilizer pentaerythritoltetrakis[3-[3,5-di- tert-butyl-4- hydroxyphenyl]propiopnate]

Preparation of HIPS Compositions and Test Specimens

The ingredients were compounded in a twin-screw co-rotating extruder(Berstorff ZE25) with L/D=32. The polymer and the additives were weighedand mixed, and the resultant blend was fed directly to the extruderport. A set temperature profile of 80-180-190-200-200-200-210-220° C.was employed. The screw speed was 350 rpm, and the feeding rate was 15kg per hour.

The extrudates obtained were pelletized in pelletizer 750/3 (AccrapacSystems Limited). The resultant pellets were dried in a circulating airoven at 75° C. for four hours.

The dried pellets were injection molded into test specimens usingAllrounder 500-150 (Arburg). The conditions of the injection molding areset out in Table 2.

TABLE 2 PARAMETER UNITS Set values T₁ (Feeding zone) ° C. 200 T₂ ° C.205 T₃ ° C. 210 T₄ ° C. 215 T₅ (nozzle) ° C. 220 Mold temperature ° C.30 Injection pressure bar 1200 Holding pressure bar 600 Back pressurebar 50 Holding time sec 7 Cooling time sec 18 Filling volume ccm 38(portion) Injection speed ccm/sec 35 Switch over point [ccm] 12

The specimens produced were conditioned at 23° C. for one week and werethen subjected to the flammability test. The compositions produced andthe results of the tests are set out in Table 3.

TABLE 3 Example 9 10 11 Composition (by weight %) HIPS 82.2 83.32581.575 FR: Compound of Formula III 12.5 13.75 16.25 Sb₂O₃ (as M-0112;containing 80% Sb₂O₃) 5 2.625 1.875 PTFE 0.1 0.1 0.1 Irganox B 225 0.20.2 0.2 Bromine content, % calculated 9 10 11.7 Antimony trioxide, %calculated 4.0 2.1 1.5 Properties Flammability test: UL-94 verticalburning test at 1.6 mm thickness Maximal flaming time (sec) 1 8 9 TotalFlaming time (sec) 10 24 46 glowing + second flaming time (sec) 50 6 0Number of Specimens dripped 0 0 0 Number of cotton ignition 0 0 0 RatingV-1 V-0 V-0

The results indicate that UL-94 V-0 rating in HIPS is attainable withthe aid of the product of Examples 1 or 3, with modest bromine contentand low antimony trioxide loading in the HIPS composition.

Examples 12 and 13 V-1 and V-0 Rated ABS Formulations

In this set of examples, the compound of Formula V (the product ofExample 5) was tested to evaluate its ability to reduce the flammabilityof ABS.

Ingredients Used to Prepare the Compositions

The materials employed in the experimental work are set out in Table 1(the abbreviation “FR” indicates flame retardant):

TABLE 4 Product (manufacturer) description function ABS Magnum 3404Acrylonitrile-butadiene-styrene plastic matrix (Styron) copolymerProduct of Example 5

FR AO 0112 Antimony trioxide masterbatch FR-synergist (Kafrit) whichcontains 80% by weight Sb₂O₃ Hostaflon 2017 PTFE Anti-dripping agent(Dyneon) Irganox B-225 50% tris(2,4-ditert- Antioxidant & heat (Ciba)butylphenyl)phosphite and 50% stabilizer pentaerythritoltetrakis[3-[3,5-di- tert-butyl-4- hydroxyphenyl]propiopnate]

Preparation of ABS Compositions and Test Specimens

The ingredients were compounded in a twin-screw co-rotating extruder(Berstorff ZE25) with L/D=32. The polymer and the additives were weighedand mixed, and the resultant blend was fed directly to the extruderport. A set temperature profile of 160-180-210-210-210-210-220-230° C.was employed. The screw speed was 350 rpm, and the feeding rate was 12kg per hour.

The extrudates obtained were pelletized in pelletizer 750/3 (AccrapacSystems Limited). The resultant pellets were dried in a circulating airoven at 80° C. for three hours.

The dried pellets were injection molded into test specimens usingAllrounder 500-150 (Arburg). The conditions of the injection molding areset out in Table 5.

TABLE 5 PARAMETER UNITS Set values T₁ (Feeding zone) ° C. 210 T₂ ° C.215 T₃ ° C. 220 T₄ ° C. 225 T₅ (nozzle) ° C. 230 Mold temperature ° C.40 Injection pressure bar 1200 Holding pressure bar 800 Back pressurebar 50 Holding time sec 7 Cooling time sec 18 Filling volume ccm 37.5(portion) Injection speed ccm/sec 30 Switch over point [ccm] 12

The specimens produced were conditioned at 23° C. for one week and werethen subjected to the flammability test. The compositions produced andthe results of the tests are set out in Table 6.

TABLE 6 Example 12 13 Composition (% by weight) ABS 81.4 80.5 product ofExample 5 13.3 17.3 Sb₂O₃ (as M-0112; containing 80% Sb₂O₃) 5.0 1.9 PTFE0.1 0.1 Irganox B 225 0.2 0.2 Bromine content, % calculated 10.0 13.0Antimony trioxide, % calculated 4.0 1.5 Properties Flammability test:UL-94 vertical burning test at 1.6 mm thickness Maximal flaming time(sec) 1 6 Total Flaming time (sec) 10 21 Maximal glow time + secondflaming 30 2 Number of Specimens dripped 0 0 Number of cotton ignition 00 Number of Specimens burning up to the clamps 0 0 Rating V-0 V-0

The results show that UL-94 V-0 rating in ABS is attainable with the aidof a combination consisting of the product of Example 5 and antimonytrioxide. The loading of the bromine-containing flame retardant and theantimony trioxide is fairly reasonable, and the UL-94 V-0 rating isachieved across a wide range of bromine: Sb₂O₃ weight ratio.

1. A process for preparing bromine-containing polymer, comprising aFriedel-Crafts alkylation reaction of tetrabromoxylylene dihalide, ortetrabromoxylylene dihalide in combination with pentabromobenzyl halide,with a reactant having one or more six-membered aromatic rings, whereinthe reaction takes place in a solvent in the presence of aFriedel-Crafts catalyst, and isolating from the reaction mixture thebromine-containing polymer.
 2. A process according to claim 1, wherein acombination of tetrabromoxylylene dihalide and pentabromobenzyl halideis used.
 3. A process according to claim 1, wherein thetetrabromoxylylene dihalide is tetrabromo-para-xylylene dibromide andthe pentabromobenzyl halide is pentabromobenzyl bromide.
 4. A processaccording to claim 1, wherein the reactant having one or moresix-membered aromatic rings is a compound of Formula (II):

where R is a linear or branched aliphatic chain; k is an integer from 0to 3; m is 0 or 1; Z is selected from the group consisting of null, O, Sand a linear or branched alkylene, whereby a bromine-containing polymerhaving a repeat unit of Formula I is obtained:

wherein R, k, m and Z are as defined above; each of al and a2 isindependently an integer from 1 to 3; each of b1 and b2 is independentlyan integer from 1 to 3, such that a₁+b₁≦3 and a₂+b₂≦3.
 5. A processaccording to claim 4, wherein the reactant is a compound of Formula IIselected from the group consisting of: toluene, where in Formula II,R═CH₃, k=1, m=0; xylene, where in Formula II, R═CH₃, k=2, m=0;ethylbenzene, where in Formula II, R═C₂H₅, k=1, m=0; diphenyl ether,where in Formula II, k=0, Z═—O, m=1; diphenylmethane, where in FormulaII, k=0, Z′—CH₂—, m=1; and 1,2-diphenylethane, wherein in Formula II,k=0, Z═—(CH₂)₂—, m=1.
 6. A process according to claim 5, wherein tolueneis reacted with tetrabromo-para-xylylene dibromide and pentabromobenzylbromide in halogenated aliphatic hydrocarbon solvent to give abromine-containing polymer comprising chains of Formula III (where nindicates the number of repeat units):


7. A process according to claim 5, wherein 1,2-diphenylethane is reactedwith tetrabromo-para-xylylene dibromide and pentabromobenzyl bromide inhalogenated aliphatic hydrocarbon solvent to give a bromine-containingpolymer comprising chains of Formula V (wherein n indicates the numberof repeat units):


8. A polymer having —CH₂C₆Br₄CH₂— and A units arranged alternately alongthe polymer backbone chain:≈≈CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A-CH₂C₆Br₄CH₂-A≈≈ wherein Acomprises one or more six-membered aromatic rings.
 9. A polymeraccording to claim 8, further comprising —CH₂C₆Br₅ side groups attachedto at least a portion of the six-membered aromatic rings of the backbonechain, wherein at least one carbon atom of said six membered aromaticring(s) is bonded to the aliphatic carbon of said —CH₂C₆Br₅ group.
 10. Apolymer according to claim 9, composed of chains represented by FormulaP:

wherein n is the number of repeat units; Ar indicates a structurecomprising one or more six-membered aromatic ring(s), wherein at leastone carbon atom of said six membered aromatic ring(s) is bonded to analiphatic carbon of the —CH₂C₆Br₄CH₂— group; where x, which indicatesthe number of —CH₂C₆Br₄CH₂— moieties in the unit, is equal to or greaterthan 1; and y, which indicates the number of —CH₂C₆Br₅ pendent groups inthe repeat unit, is 1, 2, 3, or
 4. 11. A polymer according to claim 8,having chains with repeat units represented by Formula (I):

wherein R is a linear or branched aliphatic chain; k is an integer from0 to 3; a₁ and a₂ are independently an integer from 1 to 3; b₁ and b₂are independently an integer from 1 to 3; m is 0 or 1; a₁+b₁≦3 anda₂+b₂≦3, Z is selected from the group consisting of null, O, S and alinear or branched alkylene.
 12. A polymer according to claim 11,composed of repeat units of Formula I, where m=0, R is CH₃ and k is 1.13. A polymer according to claim 12, composed of repeat units of FormulaI, where a₁=b₁=1, said polymer being represented by Formula III:

where n is the number of repeat units.
 14. A polymer according to claim11, composed of repeat units of Formula I, where m=1 and k=0.
 15. Apolymer according to claim 14, composed of repeat units of Formula IV:

wherein Z is selected from the group consisting of O, —CH₂—, and—CH₂—CH₂—, with al and a2 being independently either 1, 2 or 3 and withb1 and b2 being independently 0, 1 or 2, having bromine content of notless than 60% by weight.
 16. A polymer according to claim 15, composedof repeat units of Formula IV, where z is —CH₂—CH₂—.
 17. A polymeraccording to claim 16, composed of repeat units of Formula IV whereb1=b2=2, said polymer being represented by Formula V:

wherein n is the number of repeat units.
 18. A flame-retardedcomposition, comprising a flammable material and the bromine-containingpolymer according to claim
 17. 19.-21. (canceled)